/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.
Copyright (C) 2000-2006 Tim Angus

This file is part of Tremulous.

Tremulous is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

Tremulous is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Tremulous; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

#include "server.h"


/*
=============================================================================

Delta encode a client frame onto the network channel

A normal server packet will look like:

4 sequence number (high bit set if an oversize fragment)
<optional reliable commands>
1 svc_snapshot
4 last client reliable command
4 serverTime
1 lastframe for delta compression
1 snapFlags
1 areaBytes
<areabytes>
<playerstate>
<packetentities>

=============================================================================
*/

/*
=============
SV_EmitPacketEntities

Writes a delta update of an entityState_t list to the message.
=============
*/
static void SV_EmitPacketEntities( clientSnapshot_t *from, clientSnapshot_t *to, msg_t *msg ) {
  entityState_t *oldent, *newent;
  int   oldindex, newindex;
  int   oldnum, newnum;
  int   from_num_entities;

  // generate the delta update
  if ( !from ) {
    from_num_entities = 0;
  } else {
    from_num_entities = from->num_entities;
  }

  newent = NULL;
  oldent = NULL;
  newindex = 0;
  oldindex = 0;
  while ( newindex < to->num_entities || oldindex < from_num_entities ) {
    if ( newindex >= to->num_entities ) {
      newnum = 9999;
    } else {
      newent = &svs.snapshotEntities[(to->first_entity+newindex) % svs.numSnapshotEntities];
      newnum = newent->number;
    }

    if ( oldindex >= from_num_entities ) {
      oldnum = 9999;
    } else {
      oldent = &svs.snapshotEntities[(from->first_entity+oldindex) % svs.numSnapshotEntities];
      oldnum = oldent->number;
    }

    if ( newnum == oldnum ) {
      // delta update from old position
      // because the force parm is qfalse, this will not result
      // in any bytes being emited if the entity has not changed at all
      MSG_WriteDeltaEntity (msg, oldent, newent, qfalse );
      oldindex++;
      newindex++;
      continue;
    }

    if ( newnum < oldnum ) {
      // this is a new entity, send it from the baseline
      MSG_WriteDeltaEntity (msg, &sv.svEntities[newnum].baseline, newent, qtrue );
      newindex++;
      continue;
    }

    if ( newnum > oldnum ) {
      // the old entity isn't present in the new message
      MSG_WriteDeltaEntity (msg, oldent, NULL, qtrue );
      oldindex++;
      continue;
    }
  }

  MSG_WriteBits( msg, (MAX_GENTITIES-1), GENTITYNUM_BITS ); // end of packetentities
}



/*
==================
SV_WriteSnapshotToClient
==================
*/
static void SV_WriteSnapshotToClient( client_t *client, msg_t *msg ) {
  clientSnapshot_t  *frame, *oldframe;
  int         lastframe;
  int         i;
  int         snapFlags;

  // this is the snapshot we are creating
  frame = &client->frames[ client->netchan.outgoingSequence & PACKET_MASK ];

  // try to use a previous frame as the source for delta compressing the snapshot
  if ( client->deltaMessage <= 0 || client->state != CS_ACTIVE ) {
    // client is asking for a retransmit
    oldframe = NULL;
    lastframe = 0;
  } else if ( client->netchan.outgoingSequence - client->deltaMessage 
    >= (PACKET_BACKUP - 3) ) {
    // client hasn't gotten a good message through in a long time
    Com_DPrintf ("%s: Delta request from out of date packet.\n", client->name);
    oldframe = NULL;
    lastframe = 0;
  } else {
    // we have a valid snapshot to delta from
    oldframe = &client->frames[ client->deltaMessage & PACKET_MASK ];
    lastframe = client->netchan.outgoingSequence - client->deltaMessage;

    // the snapshot's entities may still have rolled off the buffer, though
    if ( oldframe->first_entity <= svs.nextSnapshotEntities - svs.numSnapshotEntities ) {
      Com_DPrintf ("%s: Delta request from out of date entities.\n", client->name);
      oldframe = NULL;
      lastframe = 0;
    }
  }

  MSG_WriteByte (msg, svc_snapshot);

  // NOTE, MRE: now sent at the start of every message from server to client
  // let the client know which reliable clientCommands we have received
  //MSG_WriteLong( msg, client->lastClientCommand );

  // send over the current server time so the client can drift
  // its view of time to try to match
  if( client->oldServerTime ) {
    // The server has not yet got an acknowledgement of the
    // new gamestate from this client, so continue to send it
    // a time as if the server has not restarted. Note from
    // the client's perspective this time is strictly speaking
    // incorrect, but since it'll be busy loading a map at
    // the time it doesn't really matter.
    MSG_WriteLong (msg, sv.time + client->oldServerTime);
  } else {
    MSG_WriteLong (msg, sv.time);
  }

  // what we are delta'ing from
  MSG_WriteByte (msg, lastframe);

  snapFlags = svs.snapFlagServerBit;
  if ( client->rateDelayed ) {
    snapFlags |= SNAPFLAG_RATE_DELAYED;
  }
  if ( client->state != CS_ACTIVE ) {
    snapFlags |= SNAPFLAG_NOT_ACTIVE;
  }

  MSG_WriteByte (msg, snapFlags);

  // send over the areabits
  MSG_WriteByte (msg, frame->areabytes);
  MSG_WriteData (msg, frame->areabits, frame->areabytes);

  // delta encode the playerstate
  if ( oldframe ) {
    MSG_WriteDeltaPlayerstate( msg, &oldframe->ps, &frame->ps );
  } else {
    MSG_WriteDeltaPlayerstate( msg, NULL, &frame->ps );
  }

  // delta encode the entities
  SV_EmitPacketEntities (oldframe, frame, msg);

  // padding for rate debugging
  if ( sv_padPackets->integer ) {
    for ( i = 0 ; i < sv_padPackets->integer ; i++ ) {
      MSG_WriteByte (msg, svc_nop);
    }
  }
}


/*
==================
SV_UpdateServerCommandsToClient

(re)send all server commands the client hasn't acknowledged yet
==================
*/
void SV_UpdateServerCommandsToClient( client_t *client, msg_t *msg ) {
  int   i;

  // write any unacknowledged serverCommands
  for ( i = client->reliableAcknowledge + 1 ; i <= client->reliableSequence ; i++ ) {
    MSG_WriteByte( msg, svc_serverCommand );
    MSG_WriteLong( msg, i );
    MSG_WriteString( msg, client->reliableCommands[ i & (MAX_RELIABLE_COMMANDS-1) ] );
  }
  client->reliableSent = client->reliableSequence;
}

/*
=============================================================================

Build a client snapshot structure

=============================================================================
*/

#define MAX_SNAPSHOT_ENTITIES 1024
typedef struct {
  int   numSnapshotEntities;
  int   snapshotEntities[MAX_SNAPSHOT_ENTITIES];  
} snapshotEntityNumbers_t;

/*
=======================
SV_QsortEntityNumbers
=======================
*/
static int QDECL SV_QsortEntityNumbers( const void *a, const void *b ) {
  int *ea, *eb;

  ea = (int *)a;
  eb = (int *)b;

  if ( *ea == *eb ) {
    Com_Error( ERR_DROP, "SV_QsortEntityStates: duplicated entity" );
  }

  if ( *ea < *eb ) {
    return -1;
  }

  return 1;
}


/*
===============
SV_AddEntToSnapshot
===============
*/
static void SV_AddEntToSnapshot( svEntity_t *svEnt, sharedEntity_t *gEnt, snapshotEntityNumbers_t *eNums ) {
  // if we have already added this entity to this snapshot, don't add again
  if ( svEnt->snapshotCounter == sv.snapshotCounter ) {
    return;
  }
  svEnt->snapshotCounter = sv.snapshotCounter;

  // if we are full, silently discard entities
  if ( eNums->numSnapshotEntities == MAX_SNAPSHOT_ENTITIES ) {
    return;
  }

  eNums->snapshotEntities[ eNums->numSnapshotEntities ] = gEnt->s.number;
  eNums->numSnapshotEntities++;
}

/*
===============
SV_AddEntitiesVisibleFromPoint
===============
*/
static void SV_AddEntitiesVisibleFromPoint( vec3_t origin, clientSnapshot_t *frame, 
                  snapshotEntityNumbers_t *eNums, qboolean portal ) {
  int   e, i;
  sharedEntity_t *ent;
  svEntity_t  *svEnt;
  int   l;
  int   clientarea, clientcluster;
  int   leafnum;
  int   c_fullsend;
  byte  *clientpvs;
  byte  *bitvector;

  // during an error shutdown message we may need to transmit
  // the shutdown message after the server has shutdown, so
  // specfically check for it
  if ( !sv.state ) {
    return;
  }

  leafnum = CM_PointLeafnum (origin);
  clientarea = CM_LeafArea (leafnum);
  clientcluster = CM_LeafCluster (leafnum);

  // calculate the visible areas
  frame->areabytes = CM_WriteAreaBits( frame->areabits, clientarea );

  clientpvs = CM_ClusterPVS (clientcluster);

  c_fullsend = 0;

  for ( e = 0 ; e < sv.num_entities ; e++ ) {
    ent = SV_GentityNum(e);

    // never send entities that aren't linked in
    if ( !ent->r.linked ) {
      continue;
    }

    if (ent->s.number != e) {
      Com_DPrintf ("FIXING ENT->S.NUMBER!!!\n");
      ent->s.number = e;
    }

    // entities can be flagged to explicitly not be sent to the client
    if ( ent->r.svFlags & SVF_NOCLIENT ) {
      continue;
    }

    // entities can be flagged to be sent to only one client
    if ( ent->r.svFlags & SVF_SINGLECLIENT ) {
      if ( ent->r.singleClient != frame->ps.clientNum ) {
        continue;
      }
    }
    // entities can be flagged to be sent to everyone but one client
    if ( ent->r.svFlags & SVF_NOTSINGLECLIENT ) {
      if ( ent->r.singleClient == frame->ps.clientNum ) {
        continue;
      }
    }
    // entities can be flagged to be sent to a given mask of clients
    if ( ent->r.svFlags & SVF_CLIENTMASK ) {
      if (frame->ps.clientNum >= 32)
        Com_Error( ERR_DROP, "SVF_CLIENTMASK: cientNum > 32\n" );
      if (~ent->r.singleClient & (1 << frame->ps.clientNum))
        continue;
    }

    svEnt = SV_SvEntityForGentity( ent );

    // don't double add an entity through portals
    if ( svEnt->snapshotCounter == sv.snapshotCounter ) {
      continue;
    }

    // broadcast entities are always sent
    if ( ent->r.svFlags & SVF_BROADCAST ) {
      SV_AddEntToSnapshot( svEnt, ent, eNums );
      continue;
    }

    // ignore if not touching a PV leaf
    // check area
    if ( !CM_AreasConnected( clientarea, svEnt->areanum ) ) {
      // doors can legally straddle two areas, so
      // we may need to check another one
      if ( !CM_AreasConnected( clientarea, svEnt->areanum2 ) ) {
        continue;   // blocked by a door
      }
    }

    bitvector = clientpvs;

    // check individual leafs
    if ( !svEnt->numClusters ) {
      continue;
    }
    l = 0;
    for ( i=0 ; i < svEnt->numClusters ; i++ ) {
      l = svEnt->clusternums[i];
      if ( bitvector[l >> 3] & (1 << (l&7) ) ) {
        break;
      }
    }

    // if we haven't found it to be visible,
    // check overflow clusters that coudln't be stored
    if ( i == svEnt->numClusters ) {
      if ( svEnt->lastCluster ) {
        for ( ; l <= svEnt->lastCluster ; l++ ) {
          if ( bitvector[l >> 3] & (1 << (l&7) ) ) {
            break;
          }
        }
        if ( l == svEnt->lastCluster ) {
          continue; // not visible
        }
      } else {
        continue;
      }
    }

    // add it
    SV_AddEntToSnapshot( svEnt, ent, eNums );

    // if its a portal entity, add everything visible from its camera position
    if ( ent->r.svFlags & SVF_PORTAL ) {
      if ( ent->s.generic1 ) {
        vec3_t dir;
        VectorSubtract(ent->s.origin, origin, dir);
        if ( VectorLengthSquared(dir) > (float) ent->s.generic1 * ent->s.generic1 ) {
          continue;
        }
      }
      SV_AddEntitiesVisibleFromPoint( ent->s.origin2, frame, eNums, qtrue );
    }

  }
}

/*
=============
SV_BuildClientSnapshot

Decides which entities are going to be visible to the client, and
copies off the playerstate and areabits.

This properly handles multiple recursive portals, but the render
currently doesn't.

For viewing through other player's eyes, clent can be something other than client->gentity
=============
*/
static void SV_BuildClientSnapshot( client_t *client ) {
  vec3_t            org;
  clientSnapshot_t      *frame;
  snapshotEntityNumbers_t   entityNumbers;
  int             i;
  sharedEntity_t        *ent;
  entityState_t       *state;
  svEntity_t          *svEnt;
  sharedEntity_t        *clent;
  int             clientNum;
  playerState_t       *ps;

  // bump the counter used to prevent double adding
  sv.snapshotCounter++;

  // this is the frame we are creating
  frame = &client->frames[ client->netchan.outgoingSequence & PACKET_MASK ];

  // clear everything in this snapshot
  entityNumbers.numSnapshotEntities = 0;
  Com_Memset( frame->areabits, 0, sizeof( frame->areabits ) );

  // https://zerowing.idsoftware.com/bugzilla/show_bug.cgi?id=62
  frame->num_entities = 0;
  
  clent = client->gentity;
  if ( !clent || client->state == CS_ZOMBIE ) {
    return;
  }

  // grab the current playerState_t
  ps = SV_GameClientNum( client - svs.clients );
  frame->ps = *ps;

  // never send client's own entity, because it can
  // be regenerated from the playerstate
  clientNum = frame->ps.clientNum;
  if ( clientNum < 0 || clientNum >= MAX_GENTITIES ) {
    Com_Error( ERR_DROP, "SV_SvEntityForGentity: bad gEnt" );
  }
  svEnt = &sv.svEntities[ clientNum ];

  svEnt->snapshotCounter = sv.snapshotCounter;

  // find the client's viewpoint
  VectorCopy( ps->origin, org );
  org[2] += ps->viewheight;

  // add all the entities directly visible to the eye, which
  // may include portal entities that merge other viewpoints
  SV_AddEntitiesVisibleFromPoint( org, frame, &entityNumbers, qfalse );

  // if there were portals visible, there may be out of order entities
  // in the list which will need to be resorted for the delta compression
  // to work correctly.  This also catches the error condition
  // of an entity being included twice.
  qsort( entityNumbers.snapshotEntities, entityNumbers.numSnapshotEntities, 
    sizeof( entityNumbers.snapshotEntities[0] ), SV_QsortEntityNumbers );

  // now that all viewpoint's areabits have been OR'd together, invert
  // all of them to make it a mask vector, which is what the renderer wants
  for ( i = 0 ; i < MAX_MAP_AREA_BYTES/4 ; i++ ) {
    ((int *)frame->areabits)[i] = ((int *)frame->areabits)[i] ^ -1;
  }

  // copy the entity states out
  frame->num_entities = 0;
  frame->first_entity = svs.nextSnapshotEntities;
  for ( i = 0 ; i < entityNumbers.numSnapshotEntities ; i++ ) {
    ent = SV_GentityNum(entityNumbers.snapshotEntities[i]);
    state = &svs.snapshotEntities[svs.nextSnapshotEntities % svs.numSnapshotEntities];
    *state = ent->s;
    svs.nextSnapshotEntities++;
    // this should never hit, map should always be restarted first in SV_Frame
    if ( svs.nextSnapshotEntities >= 0x7FFFFFFE ) {
      Com_Error(ERR_FATAL, "svs.nextSnapshotEntities wrapped");
    }
    frame->num_entities++;
  }
}


/*
====================
SV_RateMsec

Return the number of msec a given size message is supposed
to take to clear, based on the current rate
====================
*/
#define HEADER_RATE_BYTES 48    // include our header, IP header, and some overhead
static int SV_RateMsec( client_t *client, int messageSize ) {
  int   rate;
  int   rateMsec;

  // individual messages will never be larger than fragment size
  if ( messageSize > 1500 ) {
    messageSize = 1500;
  }
  rate = client->rate;
  if ( sv_maxRate->integer ) {
    if ( sv_maxRate->integer < 1000 ) {
      Cvar_Set( "sv_MaxRate", "1000" );
    }
    if ( sv_maxRate->integer < rate ) {
      rate = sv_maxRate->integer;
    }
  }
  if ( sv_minRate->integer ) {
    if ( sv_minRate->integer < 1000 )
      Cvar_Set( "sv_minRate", "1000" );
    if ( sv_minRate->integer > rate )
      rate = sv_minRate->integer;
  }

  rateMsec = ( messageSize + HEADER_RATE_BYTES ) * 1000 / rate * com_timescale->value;

  return rateMsec;
}

/*
=======================
SV_SendMessageToClient

Called by SV_SendClientSnapshot and SV_SendClientGameState
=======================
*/
void SV_SendMessageToClient( msg_t *msg, client_t *client ) {
  int     rateMsec;

  // record information about the message
  client->frames[client->netchan.outgoingSequence & PACKET_MASK].messageSize = msg->cursize;
  client->frames[client->netchan.outgoingSequence & PACKET_MASK].messageSent = svs.time;
  client->frames[client->netchan.outgoingSequence & PACKET_MASK].messageAcked = -1;

  // send the datagram
  SV_Netchan_Transmit( client, msg ); //msg->cursize, msg->data );

  // set nextSnapshotTime based on rate and requested number of updates

  // local clients get snapshots every server frame
  // TTimo - https://zerowing.idsoftware.com/bugzilla/show_bug.cgi?id=491
  // added sv_lanForceRate check
  if ( client->netchan.remoteAddress.type == NA_LOOPBACK || (sv_lanForceRate->integer && Sys_IsLANAddress (client->netchan.remoteAddress)) ) {
    client->nextSnapshotTime = svs.time + (1000.0 / sv_fps->integer * com_timescale->value);
    return;
  }
  
  // normal rate / snapshotMsec calculation
  rateMsec = SV_RateMsec(client, msg->cursize);

  if ( rateMsec < client->snapshotMsec * com_timescale->value) {
    // never send more packets than this, no matter what the rate is at
    rateMsec = client->snapshotMsec * com_timescale->value;
    client->rateDelayed = qfalse;
  } else {
    client->rateDelayed = qtrue;
  }

  client->nextSnapshotTime = svs.time + rateMsec * com_timescale->value;

  // don't pile up empty snapshots while connecting
  if ( client->state != CS_ACTIVE ) {
    // a gigantic connection message may have already put the nextSnapshotTime
    // more than a second away, so don't shorten it
    // do shorten if client is downloading
    if (!*client->downloadName && client->nextSnapshotTime < svs.time + 1000 * com_timescale->value)
      client->nextSnapshotTime = svs.time + 1000 * com_timescale->value;
  }
}


/*
=======================
SV_SendClientSnapshot

Also called by SV_FinalMessage

=======================
*/
void SV_SendClientSnapshot( client_t *client ) {
  byte    msg_buf[MAX_MSGLEN];
  msg_t   msg;

  // build the snapshot
  SV_BuildClientSnapshot( client );

  MSG_Init (&msg, msg_buf, sizeof(msg_buf));
  msg.allowoverflow = qtrue;

  // NOTE, MRE: all server->client messages now acknowledge
  // let the client know which reliable clientCommands we have received
  MSG_WriteLong( &msg, client->lastClientCommand );

  // (re)send any reliable server commands
  SV_UpdateServerCommandsToClient( client, &msg );

  // send over all the relevant entityState_t
  // and the playerState_t
  SV_WriteSnapshotToClient( client, &msg );

  // Add any download data if the client is downloading
  SV_WriteDownloadToClient( client, &msg );

#ifdef USE_VOIP
  SV_WriteVoipToClient( client, &msg );
#endif

  // check for overflow
  if ( msg.overflowed ) {
    //This always end fucking the server.
    //Com_Printf ("WARNING: msg overflowed for %s\n", client->name);
    MSG_Clear (&msg);
  }

  SV_SendMessageToClient( &msg, client );
}


/*
=======================
SV_SendClientMessages
=======================
*/
void SV_SendClientMessages( void ) {
  int     i;
  client_t  *c;

  // send a message to each connected client
  for (i=0, c = svs.clients ; i < sv_maxclients->integer ; i++, c++) {
    if (!c->state) {
      continue;   // not connected
    }

    if ( svs.time < c->nextSnapshotTime ) {
      continue;   // not time yet
    }

    // send additional message fragments if the last message
    // was too large to send at once
    if ( c->netchan.unsentFragments ) {
      c->nextSnapshotTime = svs.time + 
        SV_RateMsec( c, c->netchan.unsentLength - c->netchan.unsentFragmentStart );
      SV_Netchan_TransmitNextFragment( c );
      continue;
    }

    // generate and send a new message
    SV_SendClientSnapshot( c );
  }
}

